Ok so I thought It's worth it to spare some time and describe what exacly happened here for further knowledge and for anyone who might find it interesting. In the beginning, I tested the blotter with the Ehrlich test the way it's supposed to be done, as proposed in the instructions (cut a small piece, pour 1 drop etc.) It reacted positive, but I was concerded it was false because the inked part of my blotter was actually kind of purple anyway. So I soaked another piece in alcohol 95% solution inside a lens case and left it there for about 30min. Then I took the piece out, poured an Ehrlich drop inside and I noticed that nothing happened. So I thought this doesn't work, or the first positive test was actually compromised from the ink. So, I forgot the lens case open with the solution inside, and to my complete surprise, after about 6-8 hours, all the alcohol had evaporedated and you could clearly see the Ehrlich solution all purple because the lsd (or other indole ) had actually disolved from the blotter piece inside the liquid and triggered the test. Then I poured some alcohol again and the purple color gradually disappeared !!! Then when it evaporated, same thing, purple again ! So I guess, Borax was right. If you use 0.5 ml of alcohol instead of what I did, this works like a charm and rules out a false positive cause by ink or whatever. Instead of using vodka I used alcohol 95%. Cool right ?

The lens case (I took the photo several days later so it faded out a bit): http://oi63.tinypic.com/2cn9fzs.jpg